Screen with baked enamel coating



Dem 1950 F. J. GEYER 2,533,,78

SCREEN WITH BAKED ENAMEL COATING Filed Oct. 26, 194a 2 Sheets-Smart lk/w g/ W DEM: 12, 1950 GEYER 2,533,788

SCREEN WITH BAKED ENAMEL COATING Filed Oct. 26, 1948 2 Sheets- Sheet 2Mlllll u IIIE Z 126 2??? J a;

ings becoming jammed in the apertures.

Patented Dec. 12, 1950 UNITED STATES PATENT OFFICE SCREEN WITH BAKEDENAMEL COATING Fred J. Geyer, East Chicago, Ind.

Application October 26, 1948, Serial No. 56,614

6 Claims. (Cl. 209-401) This invention relates to an enameled screen.and more particularly to an enameled vibrating screen for use inscreening wet material.

This application is a continuation-in-part of my copending applicationsSerial No. 581,850, filed March 9, 1945, now abandoned and Serial No,643,591, filed January 26, 1946, now abandoned.

Considerable difficulty has been experienced in the past in thescreening of wet materials such as coal, coke, slag, limestone and thelike. The apparatus generally employed is a vibrating machine forvibrating a wire screen. The material undergoing screening oftencontains moisture and when the moisture range of the material is between12 and 25%, a problem known as "blinding arises.

Blinding occurs at a much slower rate where the free moisture content ofthe material undergoing screening is less than 12% or more than 25%, andextremely wet material will often wash through the screen without anyblind- .ing.

Blinding is the gradual closing of the underside of the screen openingsby fine particles of the material being screened. In this respect, it

should not be confused with plugging which is caused by particles largerthan the screen open- Plugging always occurs on the top of the screenand is rarely more than any annoyance. Blinding, however. will in timecompletely block the underside of the screen. When screening coal, forexample, the ordinary screen made of uncoated carbon steel wiresbecomes'completely blinded in a matter of 24 to 36 hours. At the end ofthis time, the openings between the wires will substantially all beclosed. To remove the accumulated material, it then becomes necessary toremove the screen from the machine and break loose the blindingparticles. This is generally accomplished by placing the screen upon afirm support and striking it repeatedly with a sledge. The effect of theblows generally breaks a number of wires in the screen, particularly atpoints where they are intermeshed, and as a consequence the ordinaryscreen became useless in a very short period of time.

Attempts have been made in the past to overcome the blinding tendency ofscreens by making them of stainless steel wires rather than carbonsteel. Such stainless steel screen, while not subject to blinding, isvery expensive and its use therefore has been greatly limited.

The wires of the screen are rod-like in that they are substantiallyrigid as compared with the wires in a household screen and thereforeshould have a diameter of at least inch. For heavy work the diameter maybe greater so'that the screen may be capable of supporting the weight ofthe material as it is being screened. With; a

mesh whose minimum opening is greater than inch blinding is not aseriousproblem and'li'ttle difiiculty arises. Accordingly, my invention:is directed primarily toward producing a vibratory screen consisting ofwires having diameters of at least inch and woven into a cloth having amesh size up to inch. Accordingly, there are not more than four wires tothe inch across the screen in any direction and, with inch wire, notless than 1 wires, on; the average, in at least one direction. Mypreferredscreen has a mesh whose smallest opening is from inch to inch.

I have found that by applying a hard baked enamel coating to the wiresof the screen, I can prevent blinding during the entire life of thescreen. The enamel coating must be sufliciently hard so as tohave noresidual elasticity. Softer coatings, such as paint, are notsatisfactory as minute particles of the screened material becomeembedded in the coating and permit blinding of the wires to proceed atapproximately the same rate as if no coating existed. The coating mustalso be non-porous so as to prevent even minute particles of themoisture-filled material undergoing screening from reaching the metalcomprising the wires. For this reason, galvanized Wires areunsatisfactory as a galvanized coating contains minute pores.

An enamel coating, however, which is baked on at elevated temperaturesprovides a coating sufficiently hard and non-porous as to preventblinding during the life of the screen. As the screen is vibrated at acomparatively rapid rate, abrasion takes place at the upper side of thewires and the coating on the upper side is rapidly worn off. This doesnot affect the non-blinding qualities of the screen, however, and thescreen can be used until the wires are substantially completely wornaway by abrasion. It is therefore unnecessary that the entire surface ofthe wire be coated, it being sufllcient merely to coat the underside ofthe wires. As vitreous enameling is generally carried on by dipping thescreen into a bath of the enamel, it is impractical to attempt to coatthe underside of the wires only. If the enamel is an organic enamel, forexample a phenolformaldehyde resin such as described in Hempel U. S.Patent 2,198,939, issued 'April 30, 1940, and Hempel U. S. Patent2,253,235,

assans perature of the order of 1300 to 1400 F. The

effect of subjecting the steel in the wires to such temperatures is toanneal the wires and soften the steel. However, organic resins of thetype mentioned above may be baked on at temperatures as low as 140 F.,and therefore do not affect the quality of the steel in the wires.Accordingly, I prefer to use an organic resin enamel, although both areequally satisfactory in preventing blinding of the screen. As shown byHempel Patent No. 2,253,235 these resins may contain an inorganicnon-fibrous filler.

A particular form of screen is shown in the accompanying drawings inwhich:

Fig. 1 is an end elevation of a vibratory screening machine;

Fig. 2 is a top plan view of the machine of Fi Fig. 3 is an enlargedview of a portion of the screen shown in Fig. 2;

Fig. 4 is an end view of the screen of Fig. 3;

Fig. 5 is a cross section through one of the wires of the screen showingthe baked enamel coating thereon; and

Fig. 6 is a cross section through one of the wires of the screen showingits appearance after use in the vibrating machine.

Referring now to the drawings, 10 indicates a vibratory screener havingthree screens, H, I! and I3, thereon. The screens are carried by a frameI which extends upwardly along the sides of the screens and which ismounted for horizontal movement upon a base IS. A drive wheel I6 isprovided with an eccentric l'i whereby rota-' tion of the drive wheel isadapted to vibrate the scr ens. Each screen is provided at opposite endswith metal retaining flanges l0 and is to prevent material und r oingscreening from dropping off the ends of the screen. The flanges generaltype used for screening coke and coal.

When the screening is used for screening limestone, a inch square meshis preferred. It is obvious that the size of the m sh is determined bythe particular use to which the screen is to be put. For example,'myscreen has been used for sizing and grading of soy beans in which 29diilerent sizes of mesh are used.

Baked on the outside of each wire 20 and 2| of the screen is a coatingof enamel 22. Ordinarily this coating has a thickness of about .009inch. Such thickness is sumcient effectively to prevent blinding of thescreen when used for screening wet material.

After several hours of use for the screening of hard materials, theenamel coating is entirely worn on the upper surfaces of the wires andthereafter the wires themselves are abraded away to the condition shownin Fig. 6. Even though no coating exists upon the upper portion of thewire when it has reached this condition, blinding of the screen will notoccur and the screen may continue in use until the wires are too thin tosupport the weight of the material on the screen.

By the use of my screen, it is now possible to remove fines from coal byemploying fewer vibratory machines than was heretofore necessary. Forexample, a coal screening plant which previously kept three vibratorymachines in as continuous operation as was possible with uncoated carbonsteel screens was able to halt the operation of two of those machineswhen an enameled screen of the type described in this application wasinstalled in the third machine. The amount of coal screened by the thirdmachine was greater than the amount screened by the three machinesoperated together with ordinary carbon steel screens.

I have also found that with the use of my screen it .is now feasible toscreen and grade slag, the common by-product of steel mills. Properlyscreened and graded slag has been found to be especially well adaptedfor use as a road building material, but heretofore, due to the tendencyof slag rapidly to blind any screen on which it was graded, it has beeneconomically unsound to attempt such operations.

While I have shown and described my invention in a preferred embodiment,it is to be understood that it is capable of many modifications. Changestherefore in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

I claim:

1. A vibratory screen for screening moisturecontaining materialcomprising a screen woven of high carbon steel wires having a diameterof at least A; inch, said screen having a mesh whose shortest opening isnot substantially less than inch and not substantially greater thaninch, and a coating on at least the underneath side of each of. thewires, said coating being a hard. *baked, substantially non-porousenamel coating having no residual elasticity.

2. A vibratory screen for screening moisturecontaining materialcomprising a woven wire screen with the wires being of high carbon steeland having a diameter of at least inch, said screen having a mesh ofbetween A; inch and inch and each of said wires having a bakedhard,substantially non-porous, organic enamel coating thereon, said wireshaving the tensile strength and temper of uncoated, high carbon steelwires.

3. A vibratory screen for screening moisturecontaining materialcomprising a woven wire screen with the wires being of high carbon steeland having a diameter of at least inch, said screen having a mesh whoseshortest opening is not substantially less than inch and notsubstantially greater than inch, each of said wires having a baked hard,substantially non-elastic and non-porous, heat-set resin coatingthereon.

4. A vibratory screen for screening moisturecontaining materialcomprising a woven wire screen with the wires being of high carbon steeland having a diameter of at least ,4; inch, said screen having a meshwhose shortest opening is not substantially less than inch and notsubstantially greater than inch, each of said wires having a phenolformaldehyde resin coating thereon.

. 5. A vibratory screen for screening moisturecontaining materialcomprising a woven wire screen with the wires being of high carbon steeland having a diameter of at least $4; inch, said 5 screen having a meshwhose shortest opening is not substantially less than inch and notsubstantially greater than inch, each of said wires having a hairedmncoating comprising phenol formaldehyde resin and inorganic non-fibrousfiller.

6. A vibratory screen for screening moisturecontaining materialcomprising a screen woven of steel wires having the tensile strength andtemper of non-annealed high carbon steel, said wires having a diameterof at least inch and said screen having a mesh whose shortest opening isnot substantially less than fi inch and not substantially greater thaninch, and a heatset organic enamel coating on at least the underneathside of each of the wires, said coating in its permanent applied statebeing baked hard. substantially non-porous, and being capable ofassuming its permanent applied state at temperatures below thoseannealing high carbon steel.

FRED J. GJEWER.

REFERENCES CITED The following references are of record in the file ofthis patent: I

5 UNITED STATES PATENTS Number Name Date 1,220,232 Jackson Mar. 27, 19171,693,130 Anderson Nov. 27, 1928 1,713,144 Overstrom May 14, 19291,718,386 Sherwood June 25, 1929 2,198,939 Hempel Apr. 30, 19402,334,707 Johnson Nov. 23, 1943 2,371,665 Wulfi Mar. 20, 1945 FOREIGNPATENTS Number Country Date 150,824 Australia Sept. 25, 1937 OTHERREFERENCES 20 land, Ohio, copyright 1938, pp. 5, 6 and 19.

The Making, Shaping, and Treating of Steel, 5th ed. Div. 3, by J. M.Camp and C. B. Francis, 1940, DD. 1087, 1252 and 1246, 1125 and p. 1115.

1. A VIBRATORY SCREEN FOR SCREENING MOISTURECONTAINING MATERIAL COMPRISING A SCHRREN WOVEN OF HIGH VARBON STEEL WIRES HAVING A DIAMETER OF AT LEAST 1/8 INCH, SAID SCREEN HAVING A MESH WHOSE SHORTEST OPENING IS NOT SUBSTANTIALLY LESS THAN 3/16 INCH AND NOT SUBSTANTIALLLY GREATER THAN 5/8 INCH, AND A COATING ON AT LEAST THE UNDERNEATH SIDE OF EACH OF TGHE WIRES, SAID COATING BEING A HARD,BAKED, SUBSTANTIALY NON-POROUS ENAMEL COATING HAVING NO RESIDUAL ELASTICITY. 